# -*- coding: utf-8 -*-
def fib_mun(n,mem={}) :
    if n  <= 2 :
        return 1
    
    else :
        if n-1 in mem :
            a = mem[n-1]
        else :
            a = fib(n-1,mem)
        
        if n-2 in mem :
            b = mem[n-2]
        else :
            b = fib(n-2,mem)
        
        mem[n] = a +  b
        
    return mem[n]
    
print(fib(4))